First version of the reader board. The receiver chips and the couplers on the high frequency substrate, which form the transmit-receive switch and control the circular feeding of the antenna, can be clearly seen.

Product piracy is a major problem, but embedding RFID tags in products is normally quite a difficult task. The Radar Tag project should, however, lead to the design a transponder system at 60 GHz which will allow the integration of the complete tag including the antenna on a tiny chip (1mm2).

Miniaturized RFID tag offers protection against product piracy

In a world of global trade, product piracy is extremely difficult to contain. According to VDMA estimates, the damage in Germany alone comes to 7.3 billion euro a year. Although diverse protection mechanisms exist, these are often too complex or difficult to embed in products. A lot of time and money is spent trying to trace simple tags with serial numbers or QR codes. Electronic RFID tags, on the other hand, offer cryptographically protected authentication. These, however, still operate on a near-field communication basis (NFC; 13.56 MHz) or in the UHF band (868 MHz) and therefore require large antennas that measure several centimeters. With a view to creating a much more compact RFID tag, a transponder system which operates in the 60 GHz band will be designed within the framework of the Radar Tag project so that the antenna can be fully integrated into a chip together with the digital component, the cryptography module and the power rectifier. The chip (e.g. 1 mm2) accommodates the complete tag and can easily be embedded in products. A reader at 60 GHz supplies wireless power to the tag at the time of read-out. For the purpose of information transfer, data that can be read by the reader is modulated on this signal.

Optimal solution through cooperation

The aspired transponder system is a very challenging task, not only due to the complex millimeter wave technology, but also because of the energy-saving cryptography and the sophisticated communication technique. The Fraunhofer institutes IPMS, IMS, AISEC and FHR joined forces to tackle this challenge. IPMS has the expertise necessary to realize the RFID tag, AISEC is the expert for the realization of the cryptography, IMS will provide the back end of the transponder system and FHR, with its experience in millimeter wave technology, is responsible for the read-out unit.

The challenges of creating the 60-GHz reader

The realization of the reader front end involves a number of interesting challenges. An extremely compact design is necessary to create a compact reader module in the format of a smartphone. A high transmit power, which, to the greatest extent possible, exploits the regulatory limit of 20 dBm EIRP in the far field, has to be produced for the energy supply. Energy-efficient signal generation is, of course, also necessary to reduce the space needed for cooling and energy supply to a minimum. The requirements placed on the receiver are also very demanding as this continuously receives the strong crosstalks and reflections of the 60 GHz transmit signal and, in spite of this, must work in a manner that is sufficiently linear to cleanly decode the backscatter modulation of the tag. Due to this combination of demands on the high frequency technology and the aspired, low-cost scaling for the mass market, the front end is destined for integration on a silicon-germanium chip.

A further challenge is the achievement of robust wireless communication independent of the orientation of the reader and the tag. Due to its compactness, the antennas on the tag always have a linearly polarized design. In spite of this, the signal and energy transmission should always function regardless of the orientation of the reader. To achieve rotation independent control, the transmit and receive antennas on the reader have a circularly polarized design and they are both realized in a spatially concentrated antenna.

A first version of the reader, together with an internally developed transceiver chip, has already been realized within the framework of the project. The necessary transmit power has been verified in tests and, using an internally realized dummy tag, a backscatter modulation was successfully decoded at the receiver. Due to the results achieved and the challenges that still remain with regard to the integration of the entire system, the project team is looking to the final project year with optimism and is confident that the complete system will be demonstrated successfully in 2019.